6- Two types of Analysis Methods are prevalent:
a) Static Analysis
b) Dynamic Analysis
a) Static Analysis
b) Dynamic Analysis
7- Examples of Slug flow:
a) Vacuum Transfer Lines
b) Condenser Outlet Lines
c) Re-boiler Return Lines
d) Fired Heater outlets
e) Boiler Blow down lines.
a) Vacuum Transfer Lines
b) Condenser Outlet Lines
c) Re-boiler Return Lines
d) Fired Heater outlets
e) Boiler Blow down lines.
Slug force is equal to the change in momentum with respect to time.
- Use the following equations to calculate Slug Force.
- Multiply the calculated value with a suitable DLF. Normally a DLF of 2.0 is common to use.
- Multiply the calculated value with a suitable DLF. Normally a DLF of 2.0 is common to use.
INPUTS REQUIRED FOR ANALYSIS:
* Stress isometrics of complete system.
* Line parameters such as line temperatures, pressures, fluid density, pipe material, corrosion allowance, insulation thickness, density etc.
* Parameters required for Slug force calculation like slug density or liquid density, two phase velocity etc.
* Nozzle allowable if connected to equipment.
* Stress isometrics of complete system.
* Line parameters such as line temperatures, pressures, fluid density, pipe material, corrosion allowance, insulation thickness, density etc.
* Parameters required for Slug force calculation like slug density or liquid density, two phase velocity etc.
* Nozzle allowable if connected to equipment.
ASSUMPTIONS FOR ANALYSIS:
* It is assumed that the slug is formed across the full cross section of the pipe for the maximum impact. This configuration is least probable for vertically down word flow as no hold – up is possible for accumulation of liquid and eventual formation of slug. Hence slug force at elbows for vertically downward flow lines are not considered.
* It is assumed that the reader knows normal static analysis of piping system using Caesar II.
* It is assumed that the slug is formed across the full cross section of the pipe for the maximum impact. This configuration is least probable for vertically down word flow as no hold – up is possible for accumulation of liquid and eventual formation of slug. Hence slug force at elbows for vertically downward flow lines are not considered.
* It is assumed that the reader knows normal static analysis of piping system using Caesar II.
Let’s assume the shown system is subjected to slug flow. The parameters for the pipe are as mentioned below:
• Pipe: A106B, 6”, Sch 40
• CA=3 mm
• T1=100 degree C
• T2=75 degree C
• P1=15 bar
• Liquid Density=950 Kg/m^3
• Two phase Velocity=10.53 m/s
• CA=3 mm
• T1=100 degree C
• T2=75 degree C
• P1=15 bar
• Liquid Density=950 Kg/m^3
• Two phase Velocity=10.53 m/s
After modeling the piping system following conventional method we have to calculate the slug force and apply the same into the system. Normally all organizations have their excel spreadsheet to calculate Slug Force. A typical excel spreadsheet for slug force calculation is shown in the below attached figure for your reference.
So if we use a DLF of 2 then each of axial and orthogonal force will be 4240N. We have to incorporate this force in Caesar II input spreadsheet. Check the below mentioned figure for direction of forces.
Now we will input the axial and orthogonal forces at all changes in direction as shown in attached figure.
1- To enter forces click on the Forces button in Caesar II spreadsheet.
2- Provide the node number and magnitude of forces with proper direction.
3- Similarly input forces in all bends (other than vertically downward bends).
2- Provide the node number and magnitude of forces with proper direction.
3- Similarly input forces in all bends (other than vertically downward bends).